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How do I control floating and bottom-growing algae in my lake? – Pond & Lake Q & A

No Algae Here!

Pond & Lake Q & A

Q: How do I control floating and bottom-growing algae in my lake? – Tom in New York

A: Whether it’s floating or submerged, algae can turn a lake into a green mess in no time. It’s unsightly, it’s sometimes stinky and in extreme cases, it can cause a fish kill. The good news is that algae can be controlled no matter what time of year. It starts with controlling the population and ends with a long-term management plan.

Before we dive in, it’s important to understand the difference between algae and weeds. The term “algae” refers to a wide range of single and multi-celled organisms that live in the water and metabolize carbon dioxide into oxygen via photosynthesis, just like plants. They differ from plants or weeds in that they don’t have true leaves, roots or stems.

In lakes and ponds, the most common varieties of algae include: Green floating algae that creates a “pea soup” appearance; Chara or Stonewort, which are a bottom-growing, seaweed-looking type that can be mistaken for weeds, and string or filamentous algae, which are actually long strings of algae connected together.

Sometimes, pond and lake owners may mistake duckweed for floating algae, but if you look very closely, you’ll find that it’s actually duckweed or watermeal. Check out this blog entry to learn more about controlling this invasive weed.

Population Check

If your pond is coated in pea soup or the bottom is carpeted in Chara or string algae, you can knock back the population with a chemical herbicide like Algae Defense®. It provides quick results and it’s formulated to get a pond under control – especially during the hot summer months. Do not use if your pond or lake is stocked with koi or goldfish. If your pond has trout, check your carbonate hardness with a water hardness test kit, like the Laguna® Quick Dip Multi-Test Strips, and make sure the carbonate hardness is above 50 parts per million (ppm) before using Algae Defense®.

Long-Term Strategy

Algae Defense® by Pond Logic® will solve a crisis, but to keep your pond or lake looking clean and clear, you’ll need to be proactive and develop a plan to manage the algae. The most successful approach centers on cutting off the algae’s food supply – nutrients.

Nutrients can come from a wide variety of sources, like grass clippings, twigs, trees, fish waste, yard and farm fertilizers and runoff. As these nutrients break down, they produce ammonia, which triggers the nitrogen cycle. Nitrifying bacteria surround the ammonia, turning it into nitrites and then into nitrates (nutrients) – which then feed the algae.

So, how do you reduce the nutrients in your pond?
Try these tips:

  • Buffer before fertilizing: To prevent inadvertently fertilizing the algae, leave a buffer area around the pond. You can also try using organic or low-phosphorus fertilizers.
  • Aerate, aerate, aerate: Because that muck at the bottom of the pond feeds the algae, you should prevent the buildup with proper aeration.
  • Reduce the muck: Use natural bacteria like MuckAway™ by Pond Logic® to breakdown up to 5-inches of organic muck per year. You can also rake your pond using a Pond & Beach Rake to remove dead vegetation, leaves and other organics that will eventually decompose on the bottom.
  • Reduce sunlight: Like all photosynthetic organisms, algae requires sunlight to thrive. Adding pond dye can help provide shade. If possible, consider adding some non-invasive aquatic plants to your pond. The plants, which also consume nitrates, will also be a source of competition for food.
  • Add beneficial bacteria: You may also consider adding some additional beneficial bacteria, like PondClear™ by Pond Logic®, to your pond or lake. The bacteria gobble through nitrates, breaking down fish waste, leaves and other organics that accumulate in the pond, naturally improving the water clarity.
  • That green gunk can be controlled in your pond or lake. It just takes a little planning and some proactive management. When you see the results, it’ll be worth it!

    POND TALK: When was your worst algae bloom and how did you control it?

    How do I control algae in my decorative pond, both long term and short term? – Water Garden & Features Q & A

    All Rest, No Algae.

    Water Garden & Features Q & A

    Q: How do I control algae in my decorative pond, both long term and short term?
    - Stefanie in Michigan

    A: Algae blooms are the bane of most pond owners. All summer, they rear their green heads and turn a beautiful pond or water feature into a soupy or stringy mess. But with some planning, both the floating (pea-soup algae) and filamentous (string algae) species can be controlled in the short term and prevented in the long term. Here’s how:

    Short-Term Solution

    To get your decorative pond looking clean and clear right away, you’ll need to knock down the algae population by using a chemical herbicide, like AlgaeFix or TetraPond’s Algae Control. These algae-busters are safe for use in ponds with fish, but because they destroy algae so quickly, they can cause a drop in oxygen levels in your pond, especially during the warm summer months. Be sure that your pond is adequately aerated with a fountain, waterfall or underwater air diffuser.

    Long-Term Prevention

    To prevent that green goo from surfacing again, you need to limit its food source: Nutrients. Algae thrive on nutrients, which are the end product of the nitrogen cycle. The nitrogen cycle begins with ammonia released from fish waste and detritus. Nitrifying bacteria turn the ammonia into nitrites and then into nitrates (nutrients). The algae grow, the fish eat it and excrete it, and the cycle begins again.

    So, how do you control the algae’s food source?
    Try these approaches:

  • Keep your fish load to a minimum. Most pond owners love their fish, but if they plan to have 60 12-inch koi in a 1,000-gallon pond, they’re going to have an algae problem – which can be expensive to manage. So, when calculating your fish load, think of it in pounds of fish or total inches per gallon. Remember that your fish are growing and possibly multiplying, so plan for the future and remember: Less is best. Be careful not to overstock your decorative pond.
  • Increase the number of aquatic plants. Whether they’re submerged plants like hornwort, marginals like dwarf bamboo, or floating plants like water lilies and water hyacinth, aquatic plants consume the same food that algae does – nutrients. The more plants, the more the algae have to compete for those nutrients. Floating plants also shade the pond, which filters the sunlight and can slow the growth of sun-loving algae. You should try to cover 40 to 60 percent of your pond’s surface with floaters.
  • Check the filtration. The size and type of filtration system on a pond will depend on the fish load. If the filter is not properly sized for maximum potential, the fish will outgrow the filter and produce unhealthy amounts of ammonia, which could prove lethal to the fish. An inappropriately sized filter can also cause an algae bloom from the copious amounts of nutrients in the water. In most cases, filters on the market are rated for ponds containing no fish or a minimal fish load, so you should consider a filter that is rated for at least two times the water volume of your pond.
  • Toss in some beneficial bacteria. In addition to ensuring the proper mechanical filtration, you may also consider adding some additional biological filtration – beneficial bacteria – to your pond. These hungry creatures gobble through nutrients, breaking down fish waste, leaves and other organics that accumulate in the pond. One product to try is called DefensePAC® by Pond Logic®. It’s a combination of five products that provide beneficial bacteria, trace minerals, and a fish and plant-safe pond cleaner.
  • No pond will ever be completely algae-free, but the key to keeping the green stuff under control is to limit its food supply. Like any other living thing, if it can’t eat, it can’t survive!

    POND TALK: When was your worst algae bloom, and how did you correct it?

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